Summary: This paper attempts to explore certain aspects underlying the substantial improvement in 8th grade student performance in Ghana on the Trends in International Mathematics and Science Study from2003 to 2007. The improvement was largely heterogeneous; in mathematics, performance improved more for students already performing well, while the opposite was the case for science, where students at the bottom of the score distribution experienced a spectacular increase in science scores. Most of the increase in scores for both mathematics and science is explained by over-time changes in coefficients (and a smaller part by improvements in characteristics). Contributors not accounted for (and therefore captured by changes in the constant) dominate the effects of the coefficients. One potentially important piece of information missing from the Ghana data is whether a school is private or public; this could potentially explain part of the over-time improvement. This is because over the short period between the two surveys, there was a large increase in the number of private schools in Ghana (by 36 percent between 2005/6 and 2007/8). Finally, an analysis of the over-time change in the test score gap by location (between large and small communities) revealed that the gap became more heterogeneous, narrowing for worse performing students and widening for better performing students.